1. Field of the Invention
The present invention relates to an electric double-layered capacitor using an UV-curing gel type polymer electrolyte.
2. Background of the Related Art
Generally, an electric double-layered capacitor according to a related art uses an aqueous solution based electrolyte or an organic solution based electrolyte. The aqueous solution based electrolyte includes a strong acid or strong alkaline aqueous solution having the considerably high values of ion conductivity and storage constant, thereby providing excellent characteristics of the electric double-layered capacitor. Since the strong acid or strong alkaline aqueous solution is used, development for electricity collector and components having acid resistance and alkaline resistance is demanded. Moreover, such electrolytes are unable to use at a voltage greater than the electrolysis voltage(1.23 V) of water, thereby having a low operating voltage as well as a limited range of an applicable temperature.
On the contrary, the organic solution based electrolyte has an applicable temperature range of (xe2x88x92)25xc2x0 C.xcx9c85xc2x0 C. wider than that of the aqueous solution based electrolyte as well as an operating voltage higher than 2 V. Moreover, the organic solution based electrolyte enables to use the electricity collector and components used for the secondary battery. However, when the general organic solution based electrolyte is used, there are disadvantages or problems such as low impregnation maintenance for a wide surface of an active carbon electrode used as an electrode of the electric double-layered capacitor, low attachment and adhesion between an electrode and a separating membrane, deficiency of stability due to leakage liquid, difficulty in designing and manufacturing a large-sized battery, limitation of the size and shape of battery, environmental pollution of the organic solvent, and the like.
In order to overcome the above-mentioned disadvantages or problems, many efforts are made to apply a polymer electrolyte system used widely for the previous secondary battery to EDLS.
Masashi et. al.[Electrochimica Acta, vol. 40, No. 13, 2217(1995)] have developed a gel type polymer electrolyte by adding tetraalkylammonium salt such as tetrabutylammonium perchlorate, tetraethylammonium perchlorate, tetraethylammonium tetrafluoroborate, etc. to poly(acrylonitrile)(PAN) and propylene carbonate(PC).
The gel type plasticized polymer electrolyte has a relatively-high ion conductivity under the condition that a ratio between the organic solvent and salt is optimized in a manner that the salt dissolved in the organic solvent exists in a polymer base resin having bipolar moment. Yet, a dry process is essential to prepare the gel type polymer electrolyte after a heating process at a high temperature over 100xc2x0 C. Besides, since the base resin has high viscosity at a melted state, the assembly process of the electric double-layered capacitor becomes complicated as well as the product cost increases.
Arbizzani et. al.[Electrochimica Acta, Vol. 40, No. 13, 2223(1995)] and Osaka et. al.[J. Power Sources, 74, 122(1998), J. electrochemical Society, 146, 1724(1999)] have developed the gel type polymer electrolyte by mixing poly(vinylidene fluoride)(PVdF) and poly(ethylene oxide)(PEO) with ethylene carbonate(EC) and propylene carbonate(PC) and adding the tetraalkylammonium salt to the mixture so as to fabricate the electric double-layered capacitors.
However, the report of Amand et. al.[Solid State Ionics, 94, 35(1997)] teaches that the polymer electrolyte using PEO as the base resin has high crystalline property at the room temperature just to show low conductivity as well as poor adhesion to the electrode.
Hatakimiyo et. al.(WO00/57439) introduces a substitution group having a big bipolar moment to a polyurethane molecule so as to develop a polyurethane polymer compound, which enables to maintain high conductivity and capability of dissolving an ion-conductive salt at high concentration as well as high adhesion and an interface impedance equal to that of the electrolyte solution, and a polymer electrolyte using the ion-conductive salt.
The polymer electrolyte prepared by the above-explained method is coated on a polarizing electrode by various methods, overlapped with a same polarizing electrode, and then hardened. Yet, the electric double-layered capacitor after the hardening process has poor brittleness and ductility.
Accordingly, the present invention is directed to an electric double-layered capacitor that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an electric double-layered capacitor fabricated by inserting a UV-curing gel type polymer electrolyte having excellent characteristics of ion conductivity, adhesion to electrode, compatibility with an organic solvent electrolyte, mechanical stability, permeability, and applicability to process, between electrodes.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an electric double-layered capacitor according to the present invention includes at least two electrodes and a UV-curing gel type polymer electrolyte inserted between the electrodes, the UV-curing gel type polymer electrolyte comprising a polymer material, an organic solvent or a liquid electrolyte, a UV-curing initiator, and a UV-curing accelerator, wherein the polymer material includes a function-I polymer selected from the group consisting of polyethyleneglycoldiacrylate(PEGDA), polyethyleneglycoldimethacrylate(PEGDMA), and a mixture of the polyethyleneglycoldiacrylate(PEGDA) and polyethyleneglycoldimethacrylate(PEGDMA) and a function-II polymer selected from the group consisting of a poly(vinyliden fluoride)(PVdF) based polymer, a polyacrylonitrile(PAN) based polymer, a polymethylmethacrylate(PMMA) based polymer, a polyvinyl chloride(PVC) based polymer, and a mixture of the poly(vinyliden fluoride)(PVdF) based polymer, polyacrylonitrile(PAN) based polymer, polymethylmethacrylate(PMMA) based polymer, and polyvinyl chloride(PVC) based polymer.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.